Certain clinical methods and apparatus are known in the prior art for 24 hour monitoring of intra and supra esophageal pH in patients with suspected reflux disease or laryngopharyngeal disorders.
An example of a system for ambulatory 24 hour recording of gastroesophageal reflux is the Digitrapper™ System (manufactured by Synectics Medical AB, in Stockholm, Sweden) used with glass or Monocrystant™ pH catheters (as described in U.S. Pat. No. 4,119,498) and with the analysis software EsopHogram™ (by Gastrosoft, Inc. in Dallas, Tex.). These prior art systems typically measure pH in the esophageal tract with an intra-esophageal catheter and generate reports regarding esophageal exposure of gastric fluid. Systems such as these are primarily designed to measure reflux moving past the Lower Esophageal Spincter (LES) into the esophagus.
Sensors that measure and detect reflux above the Upper Esophagel Spincter (UES) have been less successful due to problems with traditional pH sensors malfunctioning when direct fluid contact is lost. Problems such as drift and artifacts (sometimes referred to as pseudoreflux events) are common complaints when attempting to measuring pH above the UES.
Currently there are no pH monitoring devices that teach how or have the capability to simultaneously measure pH data, monitor a pH sensors level of hydration and determine the reliability of the measurement
Because all pH sensors require moisture to function, one way to determine if the sensor is functioning properly would be to detect the presence of a liquid through the use of electrical impedance. One such system as described by Anders Essen-Moller, (U.S. Pat. No. 5,479,935) detects the presence or absence of liquid reflux through the use of separate electrical electrodes incorporated into a catheter that is inserted into the esophagus. These catheters require dedicated electrodes and additional circuitry to function properly which increases cost and complexity. Additionally, because it is not directly connected to the pH sensor, it can only infer that the pH sensor is working reliably and the data is accurate if adequate levels of hydration are detected.